This invention relates in general to cleaning liquids/solids separation apparatus and, in particular, to an apparatus for cleaning materials from a filter element or filter septum. More specifically, but without restriction to the particular embodiments and/or use which is shown and described for purposes of illustration, this invention relates to a wear-compensating brush assembly for applying a predetermined force to the face of a filter element or a filter septum, to mechanically scrub the face of the filter element to remove expended filter cake and/or sludge.
As is known to those skilled in the art, various types of liquid/solid separation systems have been developed for separating solid particles from a liquid. Such systems may employ mechanical screening devices which are utilized to support a chemically adsorptive/absorptive material for separating the solids and liquid by passing the liquid through the filter element and retaining the solids materials thereon and therein. As solids materials are removed from the liquid during the separation or clarification process, these solids materials accumulate on the filter element inhibiting the continued flow of the liquid therethrough. Therefore, the clarification process must be periodically stopped and the filter material, or cake, which is formed on the filter element must be removed to enable the process to continue efficiently.
The removal of the filter material or cake from the supporting screen, or filter septum, may be done by various cleaning devices such as brushes, scrapers, or sprayers, or by methods such as vibrating, backwashing or centrifuging the elements, or a combination of such devices and methods. While some of these devices and methods may be suitable for certain purposes, they may be unsuitable for other applications causing the supporting screen or filter septum of the filter element to be damaged.
In an attempt to overcome the deficiencies of such prior art cleaning devices and methods, the present inventor developed a brush for removing filter cake and sludge from the filter septum or screen of a filter element which is the subject matter of U.S. Pat. No. 3,985,656 FILTER CLEANING APPARATUS issued on Oct. 12, 1976. This patent discloses a brush which has an arm portion mounted at an angle relative to the radii extending from the central axis of the filter element. The brush includes a plurality of flexible bristles mounted on an arm portion to form a brush for engaging the surface of the filter elements as these elements are rotated relative to the arm portion. The arm portion extends across a portion of the surface of the filter element in a particular manner such that in use materials are removed from the filter element and conveyed outwardly from the filter septum to facilitate disposal. The present invention is an improvement over such a system.
In cleaning expended filter cake from the septum of a filter element by brushing, when the brush acts against the filter cake or filter septum the abrasion which occurs results in a wearing away of the brush bristles or fibers. In many applications this wearing away occurs very slowly and is not sufficient to interfere with the liquids/solids separation process. In those applications the brush elements may be replaced during periodic maintenance of the entire equipment and, therefore, there is no loss in the efficiency or productivity of the entire system.
In applications, however, wherein the liquid material is highly viscous or gelatinous, in order to thoroughly clean the filter septum, or to remove the filter cake from the filter septum, the brush must apply a significant loading force against the filter element. In those applications the brush fibers are preferably formed from metal and the abrasion between the brush bristles and the filter element is such that a significant amount of bristle wear occurs. This high wear rate interferes with the productivity of the liquid/solids separation equipment by requiring that the clarification cycle be interrupted to permit replacement of the brush elements at intervals more frequent than periodic maintenance of the system. Therefore, it is highly desirable to provide a system wherein the useful life of the brushing elements can be increased without harming the filter elements, or interfering with the productivity of the liquids/solids separation system.